chrislloydus

Some PFC techy questions :

-Do the PIM rpm settings adjust the fuelling in addition to the
injector maps, or are the injector maps ignored when you have entries
in the PIM setting ?

-Does the PFC use the stock O2 sensor and what for ? Doesnt it use
its own maps all the time ? If it does, what is 'disable O2 feedback'
for ?

Thanks - im still learning !
Chris

yodaddy

do you have a pfc manual? if so it will tell you what disable o2 feedback means.

cewrx7r1

iTrader: (2)

The manual also explains the PIMS "CORRECTION" maps also.

chrislloydus

Youre both correct - thanks. However the information on the 02 feedback disable is 'minimal' to say the least. Ive enabled and disabled it and it doesnt seem to make much difference either way.....im guessing its for better mileage on a tank during cruising, but British roads arent designed for cruising at constant rpm - always up and down thorugh the box/rev range , so ive disabled it.

Thanks
Chris

es

O2 feedback is used at light throttle up to a certain RPM. (about 3K) It still used the map, but cycles between the map & a very lean condition (which is fine at that throttle position/RPM, & vacc level).

You don't really want to screw with disabling it because you'll be really rich when simply putting around. The Idle is easier to set really lean with out it, but the rest of the "putt mode" cells will be too rich when putting. If you lean them out then they will be too lean when you tip into the throttle & the PFC has a hard time extrapolating between a very low muliplier in the vacc cells & a normal multiplier in the low boost cells.

This is how I blew my motor. I have a log that shows the stock o2 sensor reading .15v at about 2-4PSI. Then it would come up to .93 the problem with that was when cornering at the track the throttle plates are almost closed & I was in the lean cells, then when I'd nail the gas I'd be at or reall close to the torque peak RPM point, & boom.

It could also have been the fact that the combustion chamber had hot spots from the numerous lean conditions...

YMMV
Eric.

phlanigan

Had to dig this out...

I saw that Chuck lowers the O2 feedback setting to 1.02. I'm experiencing hesitation when the PFC goes into closed-loop mode. As it cycles to lean, the car hesitates a little, and I've noticed that the PFC doesn't cycle as quickly in closed loop as the stock ECU did.

Will changing the O2 feedback settings eliminate this problem, or should I just disable O2 feedback and run a little rich? I'm a little hesitant based on ES's experience.

es

A reduction in that # should give less of a variation from rich/lean/rich/lean. I wouldn't be hesitant as I was trying to design a fuel economy map that would also work at the track with O2 feed back disabled. Problem is what is pig rich with the throttle plates barely cracked is very lean with the throttle plated Wide Open.

If your car is hesitating on the lean side of the closed loop cycle then just richen up the cells that you notice this in, & pay attention to your logs. I attribute my blown motor to my own neglagence. If I would have taken the steps to correct the lean spots I'm sure I would have been fine. But I wouldn't have a mean ported single turbo FD either...